1. Field of the Invention
The present invention relates to a technology for multiplexing and writing data based on a command from a host computer.
2. Description of the Related Art
Recently, magnetic disk devices have been used in various fields as interfaced with a host computer (upper controller) such as a digital AV device and a mobile device as well as a personal computer. As application fields of the magnetic disk devices expand, the demand for the magnetic disk devices varies.
When the magnetic disk device is used with the mobile device, for example, high reliability is more significant than large capacity because the magnetic disk device must operate in a wide variety of environments. Therefore, a magnetic disk device has been developed, which duplicates data requiring high reliability and records the data (see, for example, Japanese Patent Application Laid-open No. 2005-108040).
However, in the conventional technology, when a proportion of highly reliable data is high, it is necessary to specify duplication every time the data is recorded, which causes a troublesome problem. In particular, when the magnetic disk device has much larger capacity compared to the volume of data to be recorded, specifying duplication is more troublesome.
Also, when only a part of data is duplicated, recording capacity may change depending on a proportion of the duplicated data. Therefore, it is not possible to identify capacity of recordable data. There is another demand for recording more multiplexed data in mobile environment and the like.